Heat-recoverable articles, such as heat-shrinkable tubes and heat-shrinkable caps, are used as covering for joints between insulated electrical wires, wire terminals, metal pipes, and the like for the purpose of protection, insulation, waterproofing, corrosion protection, and the like. For example, when a joint between insulated electrical wires is covered with a heat-shrinkable tube and heating is performed, the heat-shrinkable tube shrinks, conforms to the shape of the joint, and adheres thereto, and thus the joint can be protected.
Examples of such heat-recoverable articles include a multilayered heat-recoverable article in which an adhesive layer is provided on the inner periphery of a heat-shrinkable base material layer which constitutes an outer peripheral layer. However, in the case where a copper material such as an electrical wire is covered with such a multilayered heat-recoverable article, the multilayered heat-recoverable article becomes degraded because of copper-induced damage in which copper promotes oxidation of the adhesive layer and the base material layer. Accordingly, in an existing technique, degradation of a multilayered heat-recoverable article is prevented by incorporating a copper inhibitor or an oxidation inhibitor into a base material layer which is responsible for the strength of the multilayered heat-recoverable article.
Furthermore, in order to prevent copper-induced damage, a heat-recoverable article has been proposed which includes a base material layer obtained by incorporating a six-component-based stabilizer into polyolefin (refer to Japanese Unexamined Patent Application Publication No. 6-176649).